基于改进的交叉极化比率算法的南极冻融探测

针对交叉极化比率（cross-polarized gradient ratio,XPGR）算法在冰盖冻融探测中存在的问题,提出了不依赖于实地观测数据的、自动阈值分割的、改进的XPGR微波辐射计南极冰盖冻融探测方法,即运用广义高斯模型对XPGR的长时间序列数据做直方图统计,计算出干湿雪划分的最优阈值,从而得到南极冰盖冻融分布图。试验结果表明：改进前后的结果虽然相差不多,但改进后的方法由于不依赖于实地观测数据,不仅提高了冰盖冻融探测的计算效率、实用性和可操作性,而且还在一定程度上提高了冰盖冻融探测的精度。     

1996—2021年格陵兰冰盖表面融化时空变化分析

格陵兰冰盖的表面融化通过物质平衡影响全球海平面上升,同时也是气候变化的灵敏指示器。本文基于增强分辨率的被动微波日亮温数据,使用自动气象站的气温记录,评估了进行冰盖表面融化探测的改进的亮温日较差(Advanced Diurnal Amplitude Variations,ADAV)方法和另外4种常用方法(M+30 K、ALA、MEMLS1和MEMLS2)的探测效果,通过总体精度和Kappa系数证实了ADAV方法探测冰盖表面融化的可行性与可靠性。在此基础上,基于ADAV方法进一步分析格陵兰冰盖表面融化的时空变化特征,发现1996—2021年格陵兰冰盖所有区域都发生过表面融化,融化最剧烈的区域分布于冰盖边缘,南部较北部融化范围更大、融化天数更多。极端融化事件导致冰盖融化范围波动较大,而融化指数呈现增长趋势,增长速率为5.24×10⁵ d·km²·a^-1。且表面融化具有向内陆高海拔地区扩张的趋势,融化天数为11～30 d、31～50 d、51～70 d的区域,26年间的平均高程都发生了显著的增长,增长速率分别为13.06 m·a...     

复杂地表条件下冻融土的微波辐射特性模拟及判别分析

针对AMSR-E数据的新特点,在HUT积雪辐射模型的基础上,增加冻土介电模型计算冻融土的介电常数,并使用ATEM模型描述地表的散射特性,建立寒区地表微波辐射模型,对寒区6种典型环境的微波辐射进行了模拟.结果表明:使用36.5 V的亮温以及6.925 H、10.65 H、18.7 H与36.5 V的亮温比分别衡量地表温度和发射率的变化,最能体现地表土壤的冻融变化特征.通过Fishcr判别分析,建立了复杂地表条件下的冻融土判别算法,并使用微波辐射计观测数据进行修正.AMSRE星载数据的验证结果表明,该判别算法能够有效区分较长时间序列和人范围的地表冻融状态,是种可靠的判别模式.     

冻土遥感研究进展:被动微波遥感

多年冻土和季节冻土分别占北半球裸露地表的24%和55%.近地表土壤冻融的范围、冻结起始日期、持续时间及冻融深度对寒季/寒区植物生长、大气与土壤间能量、水分及温室气体交换都具有极其重要的影响.自20世纪70年代以来,应用卫星遥感结合地面观测资料研究局地到区域尺度的季节冻土和多年冻土已取得诸多成果,而遥感在冻土研究中的最直接应用是利用微波探测近地表土壤冻融状态.相对于主动sAR,星载被动微波传感器具有多通道观测且重访周期较高,空间分辨率很低的特点.重点评述了近几十年来被动微波辐射计在冻土研究中的算法发展及其应用前景,主要包括双指标算法、时间序列变化检测算法及判别树算法3类,其核心均是基于冻土的低温特征和"体散射变暗"效应.发展可靠实用的微波遥感土壤冻融状态判别算法,提供区域和全球尺度上的土壤冻融状态信息,对水文学、气象学以及农业科学、工程地质研究与应用都具有重要意义.     

南极地区SSM/I微波辐射计亮温时间序列分析

简单介绍了微波辐射的原理与应用现状,利用美国国防气象卫星计划DMSP F系列卫星携带的SSM/I辐射计南极地区极投影网格亮温数据进行了分析与处理。结合微波亮温等温线图和南极等高线图分析了南极地区亮温分布的特点。选取8个特征区域,对1992-2000年的日亮温数据进行了时间序列分析,分析了冰盖和冰架的亮温特性、季节和年度变化、短期波动等特征。研究表明南极大陆外围冰架和南极半岛地区的亮温呈增高趋势,而内陆冰盖地区则保持相对稳定;揭示了近年来随全球气候的变暖,南极冰架和南极半岛的融化正在加剧的趋势。     

冻土遥感研究进展——可见光、红外及主动微波卫星遥感方法

多年冻土和季节冻土分别占北半球裸露地表的24%和55%。近地表土壤冻融的范围、冻结起始日期、持续时间及冻融深度对寒季/寒区的植被生长、大气与土壤间能量、水分及温室气体交换都具有极其重要的影响。卫星遥感结合地面观测资料研究局地到区域尺度的季节冻土和多年冻土已取得诸多成果。综述了近几十年来卫星遥感技术在冻土研究中的应用。监测多年冻土和地表冻融循环通常需要综合利用可见光、红外、被动微波及主动微波(包括合成孔径雷达SAR和散射计)遥感数据,任何单一波段的传感器都无法满足研究需求。SAR图像能提供空间分辨率较高的寒季/寒区近地表土壤冻融状态的起始日期、持续时间和区域演变等信息,但目前在轨SAR的重访周期相对于春秋季的土壤冻融循环变化过长;星载被动微波传感器具有多通道观测且重访周期较高,但空间分辨率很低的特点;光学和热红外传感器的时空分辨率介于SAR和被动微波遥感之间,但应用于冻土研究时需要具备多年冻土分布和冻融深度与环境因子相关关系的先验信息。总体而言,微波遥感是探测无雪覆盖近地表土壤冻融循环的有效技术手段,而利用热红外传感器反演的地表温度研究土壤冻融过程具有极大潜力。应用卫星遥感反演的积雪范围、雪深、融雪、地表类型、...     

被动微波遥感近地表土壤冻融状态数据产品对比及分析

近地表土壤冻融循环过程是陆面过程的"开关",对地表能量过程、水文过程、植被动态、温室气体交换和生态系统功能等都具有重要影响.除了依靠传统观测手段判别地表冻融,被动微波卫星遥感技术已被成熟运用于全球尺度地表冻融研究中.利用被动微波卫星遥感亮温监测地表冻融大致经历了理论基础和算法的研制、算法参数的验证和应用以及建立数据集三...     

青藏高原积雪深度和雪水当量的被动微波遥感反演

利用1993年1月份的SSM/I亮度温度数据反演了青藏高原的雪水当量,首先使用被动微波SSM/I数据19和37GHz的水平极化数据来反演雪深,根据积雪时间的函数来计算实时的雪密度,由雪的深度和密度计算出雪水当量.最后,利用SSM/I数据的19和37GHz的垂直极化亮度温度梯度对计算出的雪水当量进行回归分析,得到了利用SSM/I数据直接反演雪水当量的算法.     

两种土壤冻融判别算法在东北冻土区的判别精度评价

本文基于AMSR2被动微波数据和0 cm地表温度数据,对比分析冻融判别函数算法和双指标算法在东北冻土区的判别精度及适用性。结果表明：（1）两种算法的Kappa系数都在0.7以上,总体判别精度在87%以上,具有较好的性能。（2）两种算法在升轨时期的总体判别精度高于降轨时期。在使用升轨数据时,双指标算法判别精度略高于冻融判别函数算法;使用降轨数据时,冻融判别函数算法判别精度更高。（3）冻融判别函数算法对冻土的判别精度高,双指标算法在识别融土方面具有优势。（4）两种算法对多年冻土区的土壤冻融判别精度高于季节冻土区。本研究的评价结果可为东北冻土区制备高精度、长时序地表冻融数据集提供基础数据资料,为选择合适的土壤冻融判别算法提供参考。     

地基微波遥感评估黄河源区草原下垫面土壤冻融过程研究

土壤冻融过程对气候变化非常敏感,如何准确监测土壤冻融过程具有重要的科学意义。利用2017年6月至2018年6月中国科学院若尔盖高原湿地生态系统研究站玛曲观测场地基微波辐射计观测数据、浅层土壤温度和近地面气温数据,通过构建归一化极化比值冻结因子、极化差值冻结因子、组合水平极化差值冻结因子和组合垂直极化差值冻结因子等不同土壤冻结因子,评估了黄河源区草原下垫面土壤冻融过程。结果表明：L波段微波辐射计监测土壤冻融状态的结果与近地面气温和浅层土壤温度表征的土壤冻融过程基本一致。当入射角为50°时,归一化极化比值冻结因子和极化差值冻结因子与实测数据的一致性分别达到83.6%和82.8%。每种冻结因子具有明显的季节性变化,四种冻结因子在春季时的准确度低于夏、秋、冬三个季节。归一化后的相对冻结因子的标准差在秋季最大,可达0.3;在冬季和夏季最小,值小于0.2。在土壤发生冻结和融化转换时,垂直极化和水平极化下的亮温同时下降,其差值较完全冻结或者完全融化时的亮温差大。研究结果可为微波遥感监测土壤冻融过程提供技术参考。     

Antarctic ice-sheet near-surface snowmelt detection based on the synergy of SSM/I data and QuikSCAT data

Microwave radiometer SSM/I data and scatterometer QuikSCAT data have been widely used for the icesheet near-surface snowmelt detection based on their sensitivity to liquid water present in snow. In order to improve the Antarctic ice-sheet near-surface snowmelt detection accuracy, a new Antarctic icesheet near-surface snowmelt synergistic detection method was proposed based on the principle of complementary advantages of SSM/I data(high reliability) and QuikSCAT data(high sensitivity) by the use of edge detection model to automatically extract the edge information to get the distribution of Antarctic snowmelt onset date, snowmelt duration and snowmelt end date. The verification result shows that the proposed snowmelt synergistic detection method improves the detection accuracy from about 75% to 86% based on AWS(Automatic Weather Stations) Butler Island and Larsen Ice Shelf. The algorithm can also be applied to other regions, which provides methodological support and supplement for the global snowmelt detection.     

Distinctive petrological, geochemical, and geodynamic features of subduction-related magmatism

Geological-petrological and geochemical data on subduction-related magmatism (including the volumes and compositions of the corresponding magmatic series) are compared to the results of experiments and numerical simulation. The subduction zone is subdivided into five depth sectors and volcanic zones I, II, and III: 1 is the accretionary wedge that controls the geodynamic stability of subduction; 2 is the sector of dehydration and fluid filtration; 3 is the zone of eclogitization and initial partial melting in the slab above which boninite volcanic zone I is formed during early stages; 4 is the main zone of melting of the sedimentary-basite layer and the development of volcanic zone II with the predominance of andesites; and 5 is the zone of higher degree melting, above which volcanic zone III (basaltic andesite and alkali basalt) is formed. The criterion of volcanism intensity, which was obtained within the scope of the melting model, is proportional to the subduction velocity and the thickness of the melting zone, and the distance between the groups of volcanics along the subduction zone is 75–100 km, at a thickness of the melting zone of 15–20 km. The calculated isotherm of 600°C, which controls the stability of serpentine and chlorite, is not identified at depth above 150 km, and this is confirmed by the composition and P-T conditions of the high-pressure rocks (containing diamond and coesite), which were brought from depths of 150–200 km in subduction zones. Seismic sections constructed with regard for the amplitude characteristics of seismic waves show two melting zones (“wet” melting at a depth of 100–200 km and “dry” melting at a depth of 150–200 km) and a complicated thermal structure of the suprasthenospheric wedge, which can include slant magma conduits. The mineralogical and geochemical features of arc magmatic series are formed at a decisive role of an H₂O-CO₂ fluid and an elevated oxidation potential. The predominant buffer minerals are as follows: garnet in the slab melting zone; magnetite, Ca-pyroxene, and amphibole in intermediate magmatic chambers; and amphibole, protoenstatite-bronzite (in place of olivine), and Cr-spinel (in place of magnetite) for boninite series generated in a “hot” asthenospheric wedge at interaction with fluids or water-rich melts. Actively disputable problems are the interactions scale of melts and fluids generated in a subduction zone with a “hot” mantle wedge, the possibility of transporting water-rich minerals deep into the mantle (to depths greater than 150 km), and the evolution of the scale at which young continental crust is generated by subduction melts.     

Hot and cold zones of the Southeast Indian Ridge and their influence on the peculiarities of its structure and magmatism (Numerical and Physical Modelling)

The paper describes the specific features of the bottom topography and morphostructural segmentation along the strike of the Southeast Indian Ridge (SEIR) and in the zones of influence of the Amsterdam–St. Paul hot spot and the anomalous zone of the relatively cold mantle in the area of the Australian–Antarctic discordance. Numerical estimates of changes of thermal state and strength of the crust in axial and off-axial zones of the SEIR were performed. Сorrelation between the thermal–rheological settings in the axial zone of the ridge with the seabed topography and the morphostructural segmentation and magmatism has been established. The numerical modelling results make it possible to assume the presence of along-axis asthenospheric flows under the axial zone of the SEIR. One of them, which was initiated by the Amsterdam–St. Paul point and the Kerguelen plume, is oriented from west to east, and the second, located east of the Australian–Antarctic discordance, is oriented from east to west. Taking into account the numerical modelling results of the thermal regime and the change in thickness of the brittle layer of the axial lithosphere, we performed a physical modelling of the influence of temperature anomalies in the mantle on the peculiarities of crustal deformation in the axial zones of the ridge. The experimental modelling showed that the presence of a thermal anomaly in the sublithosphere mantle in the form of a local heat source (hot spot) will noticeably influence the geometry of the rift axis and its position in relation to the hot spot. An area of anomalous topography forms under the influence of the hot spot, traces of which are preserved in the off-axis spreading flank zones, as in the case of the Amsterdam–St. Paul hot spot. More contrasting and dissected topography forms in zones with a relatively low typical mantle temperature in the process of crustal accretion.     

Metasomatic zoning of subcratonic lithosphere in Siberia: physicochemical modeling

Nonisothermal equilibrium physicochemical dynamics has been numerically modeled to estimate the effect of reduced asthenosphere fluids on continental lithosphere profiles beneath the Siberian Platform (SP). When the over-asthenosphere continental mantle is metasomatically changed by reduced magmatic fluids, the following sequence of zones forms: (1) zone where initial rocks are intensively sublimated and depleted by most petrogenic components; the restite in this case becomes carbonated, salinated and graphitized; (2) zone of Si and Fe enrichment and carbon deposition in initial rocks depleted in Na, K, P, Mn; (3) zone of diamond-bearing lherzolites enriched with Na; (4) zone of hydrated rocks enriched with K; (5) zone of hydrated rocks not enriched with petrogenic components. Zone 1 can be responsible for the formation of kimberlite melts, zones 3 and 4 can be substrates of alkaline magma melting, and zone 5 can be the source of mafic tholeiitic magma.     

单轴压缩非贯通节理岩石尖端塑性区及弹塑性断裂模型研究

基于Drucker-Prager（下简称D-P）准则,建立压缩载荷作用下的非贯通节理岩石的弹塑性断裂模型。针对节理岩石小范围屈服翼裂纹尖端塑性区,推导了D-P屈服准则的纯I、纯II及I、II复合型3种翼裂纹无量纲塑性区径长函数,并与Mises准则的塑性区进行对比;结果表明,D-P准则的I型和复合型塑性区较Mises屈服准则的塑性区大,且其II型及I、II复合型塑性区在翼裂纹上下表面不连续。进一步,引入断裂软化因子以表征节理岩石裂隙断裂扩展后的断裂软化规律,考虑非贯通节理岩石复合型断裂软化,是由于节理尖端翼裂纹应变能密度超过最小应变能密度导致其成核扩展引起的,提出用应变能密度的指数函数形式表征断裂软化变量的演化;塑性屈服函数采用Borja等的应力张量3个不变量的硬化/软化函数,反映塑性内变量及应力状态对硬化函数的影响;建立节理岩石的弹塑性断裂本构关系及其数值算法,并用回映隐式积分算法编制了弹塑性断裂模型的程序。以单轴压缩下非贯通节理岩石为例,分析岩石断裂韧度、节理摩擦系数和节理倾角等参数的影响,结果表明,所提出的弹塑性断裂模型与数值和试验结果比较吻合。     

Automatic correction and simplification of geological maps and cross-sections for numerical simulations

Incorporating prior geological knowledge in geophysical process models often meets practical meshing challenges and raises the question of how much detail is to be included in the geometric model. We introduce a strategy to automatically repair and simplify geological maps, geological cross-sections and the associated meshes while preserving elementary consistency rules. To identify features breaking validity and/or the thin features potentially problematic when generating a mesh, we associate an exclusion zone with each model feature (horizon, fault). When these zones overlap, both the connectivity and the geometry of the geological layers are automatically modified. The output model enforces specific practical quality criteria on the model topology and geometry that facilitates the generation of a mesh with lower bounds on minimum angles and minimum local entity sizes. Our strategy is demonstrated on an invalid geological cross-section from a real-case study in the Lorraine coal basin. We further explore the impacts of the model modifications on wave propagation simulation. We show that the differences on the seismograms due to model simplifications are relatively small if the magnitude of simplifications is adapted to the physical problem parameters.     

西天山金矿遥感地质调查及重点地区金成矿条件研究

本文介绍了TM和SPOT等多源数据融合处理，以及提取蚀变影像信息和增强冻融带影像信息的方法。根据断裂构造（包括线性断裂、环状和弧形断裂构造）、地层、冻融带及蚀变带的解译，总结了西天山地区金矿成矿环境和成矿条件。在与邻区穆龙套、库姆托尔金矿对比研究的基础上，选定了重点研究地区，勾划了与金矿化关系密切的冻融带及构造蚀变带，为该区进一步开展金矿普查找和矿提供依据。     

Effect of time-evolving age and convergence rate of the subducting plate on the Cenozoic adakites and boninites

Partial melting of subducting oceanic crust expressed as high-Mg volcanic rocks such as adakites and boninites has been actively studied for decades, and Lee and King (2010) reported that time-evolving subduction parameters such as the age and the subduction rate of the converging oceanic plate play important roles in transient partial melting of the subducting oceanic crust (e.g., Aleutians). However, few subduction model experiments have considered time-evolving subduction parameters, posing problems for studies of transient partial melting of subducting oceanic crust in many subduction zones. Therefore, we constructed two-dimensional kinematic–dynamic subduction models for the Izu–Bonin, Mariana, Northeast Japan, Kuril, Tonga, Java–Sunda, and Aleutian subduction zones that account for the last 50 Myr of their evolution. The models include the time-evolving age and convergence rate of the incoming oceanic plate, so the effect of time-evolving subduction parameters on transient partial melting of oceanic crust can be evaluated. Our model calculations revealed that adakites and boninites in the Izu–Bonin and Aleutian subduction zones resulted from transient partial melting of oceanic crust. However, the steady-state subduction model using current subduction parameters did not produce any partial melting of oceanic crust in the aforementioned subduction zones, indicating that time-evolving subduction parameters are crucial for modeling transient eruption of adakites and boninites. Our model calculations confirm that other geological processes such as forearc extension, back-arc opening, mantle plumes and ridge subduction are required for partial melting of the oceanic crust in the Mariana, Northeast Japan, Tonga, and southeastern Java–Sunda subduction zones.     

考虑土体非均质传热的河岸带水热耦合模型

为弥补当前河岸带水热交换模拟对土体非均质传热考虑不足的缺陷,在饱和-非饱和渗流及多孔介质传热理论基础上,引入土体有效导热系数模型,构建考虑土体非均质传热的河岸带水热耦合模型。结合COMSOL软件的特点,给出河岸带水热耦合模型的实现方法及求解流程,并通过河岸带温度和水位原型观测资料验证和对比分析不同有效导热系数模型下河岸带水热耦合模型的模拟效果。结果表明：与传统不考虑土体非均质传热方法相比,该模型能够较好地反映河岸带水热交换过程。此外,基于Johansen有效导热系数模型的河岸带水热耦合模型模拟效果表现最佳,模拟结果与前人试验结果一致。研究成果可为河岸带水热交换及污染物迁移过程的深入研究提供技术支撑。